1. Field of the Invention
The present invention relates to a lubricating liquid separator for separating and recovering lubricating liquid from compressed gas, the lubricating liquid being used, for example, in an oil-cooled air compressor, a freezer, a gas compressor or a water lubrication type air compressor.
2. Description of the Related Art
In screw type or scroll type air/gas compressors or freezers there is used such liquid as oil or water as both lubricant and rotor coolant for rotors in a compressing section, the rotors being in contact with each other. In these gas compressors, compressed gas is discharged in a mixed state with lubricating liquid, and therefore a lubricating liquid separator for separating and recovering lubricating liquid from the compressed gas is installed in each of the gas compressors.
The lubricating liquid separator is called an oil recovering device or an oil separator in case of the lubricating liquid being oil. And the lubricating liquid separator is called a water recovering device or a water separator in case of the lubricating liquid being water. According to the principle of the lubricating liquid separator, compressed gas is introduced so as to flow along the circumferential direction from a side surface of a cylindrical housing, and there is produced rotating flow of the compressed gas along an inner wall surface of the housing. By the resulting centrifugation effect, the lubricating liquid component is gathered on the inner wall surface of the housing for separation from the gaseous component.
The compressed gas freed from the lubricating liquid to a certain extent by the centrifugation effect is discharged from the lubricating liquid separator. At this time, the remaining lubricating liquid is usually removed by a metallic or fibrous lubricating liquid removing filter called demister. The demister is known to exhibit a predetermined sound absorbing performance.
In order to let the centrifugation effect be exhibited to a satisfactory extent, the longer the rotating flow created along the inner wall surface of the housing of the lubricating liquid separator, the better. Therefore, a compressed gas inlet port for introducing the compressed gas into the lubricating liquid separator is generally formed on an upper side of the housing of the lubricating liquid separator. However, since the precipitated lubricating liquid stays in a lower portion of the housing, a compressed gas discharge port for discharging the compressed gas from the lubricating liquid separator after separation of the lubricating liquid is also formed on the upper side of the housing. In view of this point, a cylindrical partition plate having a predetermined length in the vertical direction and which surrounds the compressed gas discharge port is in many cases installed within the housing, lest the compressed gas entering from the compressed gas inlet port and containing the lubricating liquid, and the compressed gas after separation of the lubricating oil and discharged from the compressed gas discharge port should mix each other.
In Patent Literature 1 there is disclosed a separator wherein a demister is disposed inside a partition plate. On the other hand, there also is a case where a demister is disposed so as to divide the interior of the housing into two vertically without using a partition plate.
[Patent Literature 1]    Japanese Patent Laid-Open Publication No. Sho 47 (1972)-26749
However, in the separator of Patent Literature 1, a compressor pulsation noise is generated within the housing as a result of entry of compressed gas involving pressure pulsation into the housing. Consequently, the separator itself acts as a noise source, contributing greatly to an increase of noise in a gas compressor or the like.
In this connection, in Patent Literature 2 is disclosed an oil separator in an oil-cooled compressor wherein a noise damping section is provided in the interior of a vessel to reduce noise, the noise damping section having a casing which encloses a vessel-inside opening of a gas inlet section and also having a gas-permeable, heat-resistant, sound-absorbing material layer disposed at a position opposed to the opening.
In Patent Literature 3 is disclosed an oil separator wherein a member for inducing a pressure loss is disposed near a tip of a coolant inlet pipe, allowing oil contained in a mixed fluid to be adsorbed to the member, and the flow velocity of the mixed fluid is adjusted appropriately by the member, thereby suppressing noise generated upon collision of fluid with an inner wall of a vessel body.
Further, in Patent Literature 4 is disclosed an oil separator wherein a sound absorbing material is disposed at a position lower than a gas inlet port in the interior of a vessel not having a partition plate and at a position at least an upper surface of the sound absorbing material is not soaked into oil stored in an oil sump, thereby reducing generated noise. This oil separator is superior in oil separating performance and does not deteriorate the operation efficiency of the associated compressor. In this oil separator, there is disposed a demister so as to divide the interior of the vessel body into two vertically.
[Patent Literature 2]    Japanese Patent Laid-Open Publication No. Hei 8 (1996)-128388
[Patent Literature 3]    Japanese Patent Laid-Open Publication No. 2005-98534
[Patent Literature 4]    Japanese Patent Laid-Open Publication No. 2007-327439
The demister exhibits a sound absorbing performance to a certain extent, but even if the demister is disposed as in Patent Literatures 1 and 4, there is obtained little noise damping effect. Even if the demister is disposed outside a lubricating liquid separator, there will be obtained no noise damping effect, because the demister is not designed as a noise damper.
In the oil separator of an oil-cooled compressor disclosed in Patent Literature 2, an increase in the number of parts results from provision of the noise damping section within the vessel, thus giving rise to the problem of increase in cost. In the oil separator disclosed in Patent Literature 3, some improvement is needed so that the pressure loss inducing member disposed near the tip of the coolant inlet pipe may not be scattered by the discharge gas of a high pressure.
In the oil separator disclosed in Patent Literature 4, because the partition plate is not provided, scattering of the lubricating liquid after separation from the compressed gas which enters the interior of the housing is conspicuous, thus giving rise to the problem that the separation efficiency becomes lower.
Moreover, in the lubricating liquid separator which utilizes the centrifugation effect, it is necessary to enlarge the vertical length of the housing in order to enhance the separation efficiency. As a result, not only the cost of the lubricating liquid separator itself increases, but also there arises the problem of space when disposing the associated compressor body and the lubricating liquid separator within a single package.
Further, as disclosed in Patent Literature 1, if a demister is disposed inside a partition plate, there arises the problem of lowering in efficiency of the gas compressor due to an increase of pressure loss. On the other hand, if there is formed such a flow path as extends through a demister, it will be impossible to expect the demister to exhibit any noise damping effect; besides, the demister cannot play its original role.